The Fox 38 Rhythm suspension fork is engineered for aggressive trail and enduro riding, offering solid chassis stiffness and smooth damping control. However, to ensure consistent performance and longevity, it requires routine servicing and precise adjustments. This guide delivers expert-level instruction on installing, tuning, maintaining, and troubleshooting the Fox 38 Rhythm fork.

Tools Required

• 5mm and 6mm hex wrenches
• Torque wrench [paid link] (Nm scale)
• Suspension pump
• Fox Gold 20wt oil
• Isopropyl alcohol (90% or higher)
• Clean lint-free cloths
• 34mm and 38mm seal drivers
• Retaining ring pliers
• Rubber mallet
• Syringe or oil damper bleed kit [paid link]
• Digital calipers (for air shaft length confirmation)
• Fox genuine lower leg service kit (specific to 38 Rhythm)

Installation of the Fox 38 Rhythm Fork

Correct installation begins with ensuring compatibility between the fork and frame. The 38 Rhythm features a tapered steerer tube and a 15x110mm Boost axle spacing, requiring an appropriate head tube and front hub setup.

First, cut the steerer tube to the correct length based on your head tube and headset stack height. Use a pipe cutting guide to ensure a straight cut, followed by filing the edges to remove burrs. Install the star nut using a dedicated star nut setter tool, then slide the fork into the head tube.

Align the headset spacers and stem before applying even torque to the top cap and stem bolts (usually 5–6 Nm for the top cap and 6 Nm for stem pinch bolts). Finish by aligning the brake caliper, ensuring the 180mm+ post mount is correctly spaced, and route the brake hose cleanly around the crown without interference.

Adjusting the Suspension for Rider Weight and Terrain

The Fox 38 Rhythm uses an EVOL air spring and a GRIP damper, both of which allow rider-specific tuning. Begin with sag setup: the fork should compress approximately 15–20% of its total travel when the rider is seated in a neutral riding position.

Use a suspension pump to set the air pressure according to Fox’s recommended chart based on rider weight. Fine-tune by checking sag with a zip tie around the stanchion. Adjust the red rebound knob at the bottom of the right leg to control return speed. Turn it clockwise for slower rebound and counter-clockwise for faster return.

The GRIP damper’s compression adjustment is a single black dial at the top of the right leg. For climbing or smooth terrain, rotate clockwise to increase low-speed compression. For descending or rough terrain, reduce compression damping by turning counter-clockwise.

Routine Maintenance: Lower Leg Service and Lubrication

Routine maintenance is crucial to prevent premature wear. Fox recommends performing a lower leg service every 30–50 hours of riding.

Begin by removing the lower legs using a 5mm hex to undo the damper and air side bolts. Lightly tap each with a rubber mallet to dislodge the shafts. Drain old oil and clean the lower legs thoroughly using isopropyl alcohol. Inspect and replace foam rings and dust wipers if worn. Soak new foam rings in 20wt Gold oil before installation.

Use a 38mm seal driver to press new dust seals into place. Apply a small amount of suspension grease to the inside of the wipers. Reinstall the lowers carefully, ensuring proper alignment of bushings. Inject the recommended oil volume into each leg using a syringe: typically 40ml in the damper side and 20ml in the air side. Tighten shaft bolts to manufacturer-specified torque values (around 7 Nm).

Troubleshooting Common Set-Up and Performance Issues

Several common issues can affect the 38 Rhythm if not set up properly:

• Harsh compression or poor small bump compliance usually indicates excessive air pressure or too much compression damping. Recheck sag and reduce compression if needed.
• Fork not returning quickly after compression is often caused by rebound being too slow. Turn the rebound knob counter-clockwise incrementally.
• Excessive oil leakage from dust wipers can be caused by over-lubrication or damaged seals. Perform a lower leg service and inspect seals.
• Creaking sounds from the crown-stanchion interface may be the result of headset preload issues or potential crown steerer bonding issues — torque the headset and consult Fox if noise persists.

Customizing for Enhanced Performance

Though the 38 Rhythm is a budget-conscious version of the 38 Performance Elite, it can still be tailored for high performance. Upgrading to volume spacers allows riders to tune ramp-up characteristics for bigger hits. Reducing volume increases progressivity; add a spacer for more mid-stroke support.

Additionally, some riders may choose to swap the GRIP damper for the higher-end GRIP2, although this requires significant internal work and may void the warranty if not factory authorized. It’s also possible to switch the standard 170mm air spring to other travel lengths (160mm or 180mm), depending on ride preference and frame geometry constraints.

Comparing 38 Rhythm with Other Fox Models

The 38 Rhythm stands apart from the Performance and Factory models in several ways. Its chassis is shared with the top-tier models, maintaining the same 38mm stanchions and magnesium lowers. However, it lacks Kashima coating, which reduces surface friction and improves durability.

The Rhythm also comes with the simplified GRIP damper instead of the externally adjustable GRIP2. This results in fewer adjustment points, but it remains reliable and effective for most riders. Its air spring is identical to the Performance and Factory forks, which means upgrade compatibility is high.

Overall, the 38 Rhythm offers excellent stiffness and performance for the price, but riders demanding more tuning capabilities may prefer the GRIP2-equipped versions.

Compatibility with Other Drivetrain and Suspension Components

The Fox 38 Rhythm is compatible with a wide range of modern mountain bike drivetrains and braking systems. It accommodates 180mm+ rotors without adapters and supports both 29” and 27.5” wheels (depending on fork model).

It pairs best with full-suspension bikes designed for 160–180mm front travel. Ensure axle spacing matches your front hub (Boost 15x110mm). For drivetrain clearance, the fork’s arch provides ample space, but always confirm that tire size and knob profile do not interfere at full compression.

For those running handlebar-mounted lockouts, note that the GRIP damper does not support remote lockout — only the open/firm compression lever is available. This is suitable for most trail riders but may limit cross-country or race-focused tuning.

Conclusion

Servicing the Fox 38 Rhythm fork regularly and tuning it precisely for rider needs ensures maximum trail performance and longevity. From proper installation and sag adjustment to oil changes and damper tweaks, attention to detail in each maintenance step pays off in ride quality. Although it lacks some high-end adjustability, its durability and compatibility make it a smart choice for aggressive trail and enduro riders.